So what is everyones opinion on how long a 500 Hp carb motor will last. If they've had regular service (fluid changes at 20 - 30 hours). Complete valve job only 20 -25 hours ago. Total hours on motors - 510. I'm getting conflicting opinions. i've been told that the bottom ends of these motors will go a long long time....over 1000 hrs. It's the top end that's the weak link. i had a valve job done at 300 and now at just under 500 hours.

So i'd just like your opinions as to how much more life I can expect to get out of these motors.

I have to say that right now they're running better than when they were new.
I don't use any oil (the most I've had to ad between oil changes is 1/2 qrts)

Thanks everyone.

I would say from 300-500. Average 400 when taken care of. I bet I could ring 500 out of mine.

Todd, Going by the way that you maintain "Best Revenge" I would say that you have plenty of life left. Barring a mechanical failure i.e. rod, bearings, or dropping a valve......something unforseeable!! You treat her well and she'll return the favor!! I've been a auto technician for 22 years and I have a few customers that are diligent about maintenance. It shows in there odometers...929 mazda with almost 300k.....87 Dodge Van 275k......96 Roadmaster with an LT-1 motor.....almost 300k!! Keep the oil clean and talk to 'em I do!! My wife talks to the plants and I talk to my motors!!

Yup, oil , love, and being kind will keep them alive. I never beat my stuff, I may make a short burst at WOT but for seconds. I don't care about top speed, it can't be sustained so who cares. I keep it at 3500-4000 and they love me for it.

I'd really appreciate to know what a marine mechanic or engine builder might have to say about this.

I'm at 500 hours now......I'm sure, in fact I know I have a tremendous amount of life left in the bottom end of these things. I know its the top end thats the weak point. So when they need it I'll rebuild the valve train again. shouldnt need it done for 200 - 300 hours from now.

Thanks

Ive gotten 4000 hours out of a 454-330hp in a well taken care of parasail boat, that saw some hard use,with out getting into them and thats in salt water.Only thing that will kill them fast is overheating them and if you do catch it in time turning it off and changing the oil before hard running.I dont know about 500s but I agree wot for any length of time is hard on any motor.